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Water splitting through electrolysis has been recognized as a promising solution for the production of hydrogen and oxygen to advance many renewable energy conversion and storage systems, while the key is the innovative exploration of cost-efficient electrocatalysts. Herein, interface-modified Ni–Fe–P/Co–P/NF alloys were achieved through a facile electroless plating strategy, in which the constructed interfaces benefited not only from the strong electron interaction but also from the fast mass transfer, significantly boosting the oxygen evolution reaction and hydrogen evolution reaction catalytic performance. More interestingly, water-splitting cells assembled using Ni–Fe–P/Co–P/NF-5L alloys as the cathode and anode, respectively, only requires a cell voltage of ∼1.52 V at 10 mA cm–2, far lower than that of the integrated Pt–C/NF and RuO2/NF couple (1.61 V). Also, the Ni–Fe–P/Co–P/NF-5L||Ni–Fe–P/Co–P/NF-5L system shows an outstanding durability over a long-term operation of 48 h at 10 mA cm–2. The work demonstrates an innovative strategy to construct heterogeneous interfaces for high-performance electrocatalysts and is suggested to be readily extended to regulate heterogeneous interfaces among other binary and ternary electrocatalysts, such as transition metal phosphides/borides, for scaling up water-splitting technology.

ABSTRACTThis study investigates the impact of current density on the microstructure, composition, and internal stress of Ni-W alloys electrodeposited in a citrate system. Using XRD, SEM, EDS, TEM, and XPS, it was found that tungsten serves as a solute in a Ni-W FCC structure oriented in the (111) direction. Increasing current density led to higher tungsten content and current efficiency. The addition of 2-Butyne-1,4-diol altered the carbon content, significantly reducing internal stress by promoting carbide formation near grain boundaries, which prevented coating shrinkage during hydrogen escape. This carbon enrichment improved the alloy's corrosion resistance.

This study investigates the impact of current density on the microstructure, composition, and internal stress of Ni-W alloys electrodeposited in a citrate system. Using XRD, SEM, EDS, TEM, and XPS, it was found that tungsten serves as a solute in a Ni-W FCC structure oriented in the (111) direction. Increasing current density led to higher tungsten content and current efficiency. The addition of 2-Butyne-1,4-diol altered the carbon content, significantly reducing internal stress by promoting carbide formation near grain boundaries, which prevented coating shrinkage during hydrogen escape. This carbon enrichment improved the alloy's corrosion resistance.

Electrolysis of water to generate hydrogen is an important issue for the industrial production of green and sustainable energy. The best electrocatalyst currently available for the hydrogen evolution reaction (HER) is platinum. We herein show that iridium can be manipulated to achieve a record high HER activity surpassing platinum in every aspect: a lower overpotential at any given current density, a higher current density, and mass activity for all bias potentials applied and a catalyst cost reduction of 50% for the same hydrogen generation rate. The superior HER activity was achieved by a binary Ir/Si nanowire catalyst design in which (as density functional theory calculations show) two distinct strategies act in synergy: (i) decreasing the size of the iridium nanoparticles to ∼2.2 nm and (ii) dividing the H2-generation process to three steps occurring on two different catalysts: H adsorption on iridium, H diffusion to silicon, and H2desorption from silicon.

In this paper, Ni-Co coatings were electrodeposited onto carbon steel substrates with the aid of ultrasonic agitation. The coatings were analyzed by energy dispersive X-ray analysis (EDX), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The effects of the ultrasonic frequency on the roughness, hardness and corrosion resistance of the Ni-Co coatings were also investigated. The results indicated that the increase of the ultrasonic frequency from 20 to 120 kHz reduced the Ni content and the grain size of Ni-Co coatings. Moreover, the phase structure of the electrodeposited coatings was influenced by the ultrasonic frequency. Under 55 kHz ultrasonic agitation, the Ni-Co coating was single fcc phase and showed the finest roughness and the strongest corrosion resistance in 5 wt.% NaCl solution at the ambient temperature. Under ultrasonic agitation with frequency of 90 kHz, the coating was a mixture of fcc and hcp structure and showed the maximal hardness of about 420 HV. Therefore, ultrasonic agitation helped decrease the roughness, and enhance hardness and corrosion resistance of Ni-Co coatings.

Electrocatalytic water splitting is a desirable and sustainable strategy for hydrogen production yet still faces challenges due to the sluggish kinetics and rapid deactivation of catalysts in the oxygen evolution process. Herein, we utilized the metal-catalyzed growth technology and phosphating process to fabricate self-supported electrodes (CoxPy@CNT-CC) composed of carbon nanotube (CNT) arrays grown on carbon cloth (CC); thereinto, cobalt-based phosphide nanoparticles (CoxPy) are uniformly encapsulated in the cavity of the CNTs. After further optimization, when the nanoparticles are in the composite phase (CoP2/Co2P), CoP2/Co2P@CNT-CC served as catalytic electrodes with the highest activity and stability for electrocatalytic water splitting in an alkaline medium (1.0 M KOH). The as-prepared CoP2/Co2P@CNT-CC integrates the advantages of the abundant active sites and confinement effect of CNTs, imparting promising electrocatalytic activities and stability in catalyzing both hydrogen evolution reaction and oxygen evolution reaction. Remarkably, electrocatalytic water splitting cells assembled using CoP2/Co2P@CNT-CC electrodes as the cathode and anode, respectively, require a cell voltage of 1.55 V at 10 mA cm–2, which is lower than that of the commercially noble Pt/C/CC and RuO2/CC catalyst couple (1.68 V). Besides, a CoP2/Co2P@CNT-CC||CoP2/Co2P@CNT-CC system shows outstanding durability for a period of 100 h at 10 mA cm–2. This work may provide new ideas for designing bifunctional electrocatalysts for applications in electrocatalytic water splitting.

Abstract: The influence of dissolved ozone (O3) and its concentrations on the formation of phosphate coatings on carbon steel in phosphate bath, as well as the protective properties of phosphate coatings in a 5 wt% NaCl solution have been studied. The structure, surface morphologies, and phase compositions of the phosphate coating on the carbon steel substrate was investigated by SEM, XRD. It is shown that the phosphate coating became more dense with fewer microholes and an increasing concentration of ozone in phosphate bath in the range of 0.0 to 1.62 mg/L. The coating compositions were Zn3(PO4)2 · 4H2O (hopeite) and Zn2Fe(PO4)2 · 4H2O. Potentiodynamic polarization and immersion tests were used to evaluate the corrosion properties of the treated samples. The coating showed good corrosion resistance properties.